The invention relates to acid-stable polycarboxylic acids, to a process for their preparation by oxidative cleavage of double-bond compounds with hydrogen peroxide or hydrogen peroxide donors, to the use of the polycarboxylic acids for treating cellulosic fibres or textile or paper materials produced therefrom and to the thusly treated cellulosic fibres, textile materials or paper materials.
Textiles made of cellulosic fibres such as cotton have the advantage over synthetic fibres of being hydrophilic, which manifests itself in high moisture absorption and good wear comfort. The reason for the high moisture absorption is the swellable amorphous regions in cellulosic fibres. However, cellulose swollen by washing or perspiration wrinkles and has to be smoothed again by thermal and mechanical treatment. In addition, cotton shrinks on washing, causing textiles to lose their original shape. To control these disadvantages, cellulosic fibres have for many years been treated with products which, by reacting with the hydroxyl groups of the cellulose, partly crosslink the amorphous parts of the fibres. Owing to this treatment, the textile retains its shape on wearing and washing. Preferred crosslinkers are methylolated urea or melamine derivatives. The disadvantage with these compounds is that they may release formaldehyde in the course of the finishing and use of the textile.
There has therefore been no shortage of attempts to find alternative and ecologically better products for treating textiles. The use of polycarboxylic acids such as butanetetracarboxylic acid for formaldehyde-free textile finishing is known in principle from Text. Res. J. 37, 933 (1967) and U.S. Pat. No. 4,820,307.
It is likewise already known in principle that polycarboxylic acids may be prepared by oxidative cleavage of compounds containing double bonds. For instance, butanetetracarboxylic acid can be prepared by oxidative cleavage of tetrahydrophthalic acid using nitric acid under vanadium catalysis (J. Org. Chem. 30, 1488 (1965), DE-A-30 16 225, JP 59128350 A2). This process is disadvantageous because of the aggressive reaction conditions causing some of the starting materials used and of the intermediate and end products to be decomposed by further oxidation reactions. In addition, toxic nitrogen oxides escape in the course of the reaction and can only be removed by an inconvenient gas scrub. The process by-produces nitrogenous compounds which, in the use as textile crosslinkers, lead to noticeable yellowing of the finished fabric and are removable only by inconvenient recrystallizing.
Therefore, hydrogen peroxide is a more suitable oxidizing agent, since its use gives rise to just water as reaction product. U.S. Pat. No. 3,646,130 describes the oxidative cleavage of cyclododecene with hydrogen peroxide using Re2O7 as catalyst. EP-A-0 122 804 discloses the oxidative cleavage of various olefins with hydrogen peroxide using a catalyst prepared from H2WO4, H3PO4 and a phase transfer catalyst. In EP-A-0 123 495 various intermediates obtainable by dihydroxylation of olefins are cleaved to the corresponding carboxylic acids using hydrogen peroxide and a catalytic system composed of H2WO4 and H3PO4.
EP-A-0 513 600 describes preparing carboxylic acids by oxidative work-up of olefins reacted with ozone. This reference too mentions preparing butanetetracarboxylic acid from tetrahydrophthalic anhydride. But the disadvantage with this process is the use of toxic ozone, which, moreover, is energy-intensive to prepare.
U.S. Pat. No. 5,047,582 describes the preparation of polycarboxylic acids in a two-step process. The first step is the conversion, in a non-catalyzed process, of an olefin into the corresponding dihydroxy compound which, in a second step, is cleaved by the use of various transition metal catalysts into the corresponding polycarboxylic acid.
EP-A-0 201 719 discloses preparing polycarboxylic acids such as butanetetracarboxylic acid by oxidative cleavage of olefins such as tetrahydrophthalic anhydride with hydrogen peroxide using a catalyst selected from tungstic acid, molybdic acid and heteropolyacids thereof.
EP-A-0 688 897 describes the oxidative cleavage of tetrahydrophthalic anhydride with hydrogen peroxide to form butanetetracarboxylic acid and also the use of the thusly obtained butanetetracarboxylic acid for treating cellulosic fibres.
JP 08295649 A2 describes preparing butanetetracarboxylic acid by using tungsten compounds combined with nitrogenous heterocyclic carboxylic acids as oxidation catalysts.
One disadvantage with the above-described background art is that the butanetetracarboxylic acid obtained does not possess adequate acid stability in the aqueous reaction solutions produced. The consequence is that some of the butanetetracarboxylic acid separates as a solid, the rest remaining dissolved in the aqueous phase. But such solids-containing solutions are unsuitable for treating fibres or textile materials. The butanetetracarboxylic acid therefore has to be first completely isolated by evaporating the water. This, however, is energy-intensive and hence not economical. In addition, crosslinkers in the form of solids are not very attractive; the most commonly used crosslinkers for cellulose are offered as aqueous solutions because of their better handlability. These disadvantages are the reason why polycarboxylic acids such as butanetetracarboxylic acid have hitherto not found commercial application for finishing cellulosic fibres or textile materials produced therefrom.
It is accordingly an object of the present invention to provide a process for preparing polycarboxylic acids that possess sufficient acid stability in aqueous solution and are suitable for crosslinking cellulosic fibres.
This object is achieved by a process for preparing polycarboxylic acids by
1) reacting compounds of the formulae (I) or (II) 
where
R1 and R2 are identical or different and each is H or straight-chain or branched C1-C5-alkyl,
with compounds of the formula (III)
R3XHxe2x80x83xe2x80x83(III) 
where
x is O, NH or S and
R3 is straight-chain or branched C1-C30-alkyl, straight-chain or branched C2-C30-alkenyl, C5-C12-cycloalkyl, xe2x80x94CHR4COOH
xe2x80x83where
R4 is H, straight-chain or branched C1-C5-alkyl, xe2x80x94CH2OH, xe2x80x94CH(OH)COOH or xe2x80x94CH2COOH,
xe2x80x83or
xe2x80x94(CH2CR5R6Y)nR7,
where
Y is O or NR8,
R5, R6, R7 and R8 are independently H, straight-chain or branched C1-C4-alkyl, xe2x80x94CH2OH or xe2x80x94CH2CH2OH and
n is an integer from 1 to 20
and
2) subsequent oxidation in the presence of hydrogen peroxide or of a hydrogen peroxide releaser and of a catalyst.
The invention further provides the polycarboxylic acids obtainable by this process.
The reactants used in the process of the invention are compounds of the formulae (I) or (II). They are tetrahydrophthalic acid, tetrahydrophthalic anhydride or appropriately substituted derivatives thereof. R1 and R2 are identical or different and are each preferably hydrogen or methyl in the formulae (I) and (II). Particular preference is given to using 1,2,3,6-tetrahydrophthalic anhydride for the reaction with compound (III).
The compounds of the formula (III) used in the process of the invention can be monofunctional, bifunctional, trifunctional or more highly functional, depending on which of the indicated meanings are assigned to R3.
Preference is given to using at least bifunctional compounds of the formula (III) where
X is O and
R3 is xe2x80x94CHR4COOH,
where
R4 is H, straight-chain or branched C1-C5-alkyl, xe2x80x94CH2OH, xe2x80x94CH(OH)COOH or xe2x80x94CH2COOH, or xe2x80x94(CH2CR5R6Y)nR7,
where
Y is O or NR8 and
R5, R6, R7 and R8 are independently H, straight-chain or branched C1-C4-alkyl, xe2x80x94CH2OH or xe2x80x94CH2CH2OH and
n is an integer from 1 to 10, preferably from 1 to 5.
Particular preference for use as bi- or trifunctional compounds of the formula (III) is given to the use of ethylene glycol, diethylene glycol, triethylene glycol, lactic acid, glycerol, trimethylolpropane or 2,2-bis(hydroxymethyl)propionic acid.
In a preferred embodiment, 1,2,3,6-tetrahydrophthalic anhydride is reacted with an R3OH compound where R is xe2x80x94(CH2CR5R6Y)nR7, Y is O or NR8 and R5, R6, R7 and R8 are independently H, straight-chain or branched C1-C4-alkyl, xe2x80x94CH2OH or xe2x80x94CH2CH2OH and n is an integer from 1-20, preferably 1-10, especially 1 to 5.
In a particularly preferred embodiment, 1,2,3,6-tetrahydrophthalic anhydride is reacted with an R3OH compound where R3is (CH2CH2O)nH and n is an integer of 1 to 5, preferably 1, 2 or 3.
The reaction of compounds (I) or (II) with compound (III) in step 1) of the process according to the invention is carried out at a temperature of 50 to 250xc2x0 C., preferably 90 to 150xc2x0 C., and a pressure of 0 to 10 bar, preferably 0.5 to 2 bar. The reaction time is customarily 0.5-24 hours, preferably 1 to 3 hours. The reaction is preferably carried out in stirred vessels and reactors. The compounds (I) or (II) and (III) can be added in any order, preferably not in solution but as solids or liquids. The reaction can be carried out in the presence but also in the absence of a catalyst. If a catalyst is used, customary esterification catalysts, such as acids or bases, or metallic catalysts, such as titanium or tin compounds, are useful.
The as-reacted mixture of step 1) is subsequently and directly subjected, in step 2), to an oxidative cleavage using hydrogen peroxide, or a compound that releases hydrogen peroxide in situ, as oxidizing agent. Prior to the oxidative cleavage a work-up of the reaction mixture is advantageously not necessary, but can be carried out.
The oxidation in step 2) of the process according to the invention constitutes an oxidative cleavage of the double bonds in the reaction products of step 1) to form two carboxylic acid groups at two adjacent carbon atoms which are then linked by a single bond. This oxidation is carried out in the presence of a catalyst. The catalyst used is preferably a tungsten or molybdenum catalyst. Examples of suitable tungsten catalysts are tungsten oxide (WO3), tungstic acid (H2WO4 or WO3.H2O), the isopolyacids and heteropolyacids of tungsten, alkali metal, alkaline earth metal and ammonium tungstates, preferably sodium tungstate (Na2WO4.2H2O), ammonium paratungstate ((NH4)10W12O41.11H2O) or ammonium metatungstate ((NH4)6H2W12O40). Examples of suitable molybdenum catalysts are molybdenum(VI) oxide, the isopolyacids and heteropolyacids of molybdenum and also alkali metal, alkaline earth metal or ammonium molybdates.
The oxidizing agent used is hydrogen peroxide or a compound that donates hydrogen peroxide in situ. As compounds donating hydrogen peroxide in situ there can be used hydrogen peroxide addition compounds such as peroxide-urea adducts or per compounds such as perborates, percarbonates or persulphates in the form of their alkali metal salts, individually or in mixtures. Preference is given to using a hydrogen peroxide solution 30 to 60% by weight in strength. Particular preference is given to using a commercially available 50% by weight hydrogen peroxide solution.
The oxidative cleavage is carried out at a temperature of 50 to 150xc2x0 C., preferably 70 to 95xc2x0 C., and a pressure of 0 to 4 bar, preferably 0.5 to 2 bar. The reaction time is customarily 0.5 to 24 hours, preferably 3 to 10 hours. The reaction is customarily carried out in a stirred vessel or reactor. The hydrogen peroxide or the hydrogen peroxide releaser is customarily simply added to the reaction mixture from the first step of the process according to the invention.
The present invention provides the polycarboxylic acids obtainable by the aforementioned process. They are obtained as described in aqueous solution after the oxidative cleavage and can advantageously be used without further work-up for durable press finishing of cellulosic fibres or textile materials produced therefrom. However, it is also possible to isolate the polycarboxylic acids by evaporating the water or by precipitation.
The advantage of the polycarboxylic acids thus obtained is that they are readily water-soluble and acid-stable, ie. they are stable to precipitations even at low temperatures, unlike butanetetracarboxylic acid. The pH of the polycarboxylic acid solution obtained after step 2) of the process according to the invention is in the range from 0 to 2, but preferably the pH is not more than 1. Depending on the intended purpose, the pH of these polycarboxylic acid solutions can be adjusted with alkaline compounds to a pH of up to 10, preferably to a pH in the range from 3 to 5.
Depending on whether the compound of the formula R3XH used in the process of the invention is mono-, bi-, tri- or more highly functional and depending on the molar ratio in which the compounds of the formula (I) or (II) are used relative to the compounds of the formula (III), polycarboxylic acid mixtures can be formed in the reaction.
The use of a monofunctional R3XH compound produces via the intermediate of the formula (IV) 
where either one Z is OH and one Z is XR3 or both are XR3, the di- or tricarboxylic acids of the formula (V) 
The use of a bifunctional R3XH compound where X is O, NH or S gives rise to a substantially larger number of possible polycarboxylic acids. When R3 is, for example, (CH2CR5R6Y)nH, where Y is O or NR8 and R5, R6 and R8 are independently H or straight-chain or branched C1-C4-alkyl and n is an integer from 1 to 20, preferably 1 to 10, particularly preferably 1 to 5, and the compound of the formula (I) or (II) is used in a molar ratio of 2:1 relative to the compound (III), the intermediate product has the formula (VI) 
where
X is O, NH, or S,
Y is O or NR8,
R5, R6 and R8 are independently H or straight-chain or branched C1-C4 alkyl and
n is an integer form 1 to 20, preferably 1 to 10, particularly preferably 1 to 5, and gives rise as the main product to the hexacarboxylic acid of the formula (VII) 
where
X, R5, R6 and Y have the meanings already above mentioned for this variant.
The invention further provides for the use of the polycarboxylic acids obtainable by the process of the invention for finishing cellulosic fibres or textile or paper materials produced therefrom. Here, the polycarboxylic acids of the invention are preferably used directly in the form of the aqueous solutions that are obtained according to the process of the invention.
The invention further provides a process for finishing cellulosic fibres or textile or paper materials produced therefrom, characterized in that the cellulosic fibres or textile or paper materials produced therefrom are treated with an aqueous liquor containing the polycarboxylic acids according to the invention with or without catalysts and textile auxiliaries, preferably softeners, hand modifiers, hydrophobicizers, oleophobicizers, flame retardants or pH regulators.
By reacting with the hydroxyl groups of the cellulose, the polycarboxylic acids of the invention crosslink the amorphous parts of the fibres to some extent. This no-wrinkle and no-iron finish ensures that the textile retains its shape on wearing and washing.
Catalysts useful in the finishing of cellulosic fibres or textile or paper materials produced therefrom include for example alkali metal hypophosphites and alkali metal phosphites, preferably sodium hypophosphite or sodium phosphite. Such alkali metal hypophosphites and alkali metal phosphites are described in U.S. Pat. No. 4,820,307. Useful catalysts further include cyanamide or a compound of the formula (VIII) 
where
Rxe2x80x2 is NH, O or S
and
Rxe2x80x3 is CN or H.
Cyanamide and the compounds of the formula (VIII) are described in U.S. Pat. No. 5,205,836.
The liquor treatment of cellulosic fibres or of textile or paper materials produced therefrom can be effected according to methods familiar to one skilled in the art, such as pad-mangling, spraying, kiss rolling or foaming. The liquor used customarily contains 10 to 100 g of active ingredient per liter, preferably 30 to 70 g of active ingredient per liter.
After application has taken place, the cellulosic fibres or textile or paper materials produced therefrom are dried at temperatures of 100 to 130xc2x0 C. This drying is preferably carried on to reach a residual moisture content of 1 to 10% by weight, preferably 2 to 6% by weight, especially 3 to 4% by weight. This is followed by a heat treatment at temperatures of 130 to 220xc2x0 C., preferably 140 to 180xc2x0 C. The steps of drying and heat treatment can also be carried out in a single stage.
The process of the invention is useful for treating any cellulosic fibres or textile or paper materials produced therefrom. Useful cellulosic fibres include for example textile fibres of natural or regenerated cellulose or of cellulose acetate. The process can also be used for finishing blends of cellulosic and synthetic fibres. Examples of substrates which are treated are cotton, linen, rayons or paper.
The invention thus also provides cellulosic fibres or textile or paper materials treated with the polycarboxylic acids according to the invention.